Copper is a conductive material and is used in various fields, for example, a semiconductor integrated circuit, an opto-electronic communication field, and a micro-electro mechanical system (MEMS). Copper may be used as a seed layer for forming a metal layer or a metal interconnection along with aluminum, chromium, or titanium in a semiconductor device. Thus, semiconductor processes for forming a semiconductor device may need a process of selectively etching a metal layer including copper.